When Jack died in The Parting of the Ways, Rose brought him back to be a fixed point in time and space. So, if we take a space-time graph and plot a normal person's life on it, we would get something like this:

Space-time graph

But for ol'Jackie, it would be more like this:

enter image description here

and the assumption is that whenever he strays too far from that point, i.e., dies or is injured, he's dragged back there kicking and screaming. I'm basing that assumption mainly on this and a few other question here. And short of that one joke about grey hair and vanity, there is no indication that he even ages.

The point being that he can't change physically.

But what about emotional and psychological change?

Having been alive for I don't know how long since he was revived, could he have changed as a person, or would the power of Rose's immortalization drag him back to the same person he was at the time he died aboard the Game Station?

Because considering what is shown in both series, he doesn't seem to have grown as much as you would expect a person to considering what all he went through.

Canonical answers from other media would be appreciated, but anything within reason and logic (acceptable Doctor Who logic) would work.

2 Answers 2


Jack seems remarkably impervious to both physical and psychological changes over time.

The best example I can think of regarding his mental state is Torchwood : Exit Wounds where we see Jack being buried in 29AD and subsequently disinterred in 1901 AD.

Despite having been trapped underground for nearly two millennia, suffering the untold agony of repeatedly being reborn and then suffocating to death (potentially millions of times) within seconds he's able to function completely normally and seems to have no adverse side-effects whatsoever.

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    I always chose to interpret this as horrible writing, but in-universe I suppose this is as valid a theory as anything else. Aug 14, 2014 at 11:13
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    Doesn't gaining new memories/knowledge count as physical change? Then again, if he literally stayed at the same state for eternity, he would make for a terrible character.
    – calccrypto
    Aug 14, 2014 at 11:44

Jack can undergo substantial physical changes, culminating in his physical appearance at the end of his massively extended but not infinite life, when he becomes:

(Series 3 spoilers ...)

The Face of Boe Jack is the Face of Boe

Given that this is his original appearance when the Bad Wolf brings him "back" to life:

Capt. Jack Harkness

There is further evidence to support the claim that these individuals are the same:

Despite the revelation in Last of the Time Lords, the actual origin of the Face of Boe is still debated, with Davies himself waffling during the commentary for the episode as to whether Jack really is destined to become the Face of Boe. Producer Julie Gardner, however, has been more assertive in this regard, most recently stating outright at the 2008 San Diego Comic Con that the Face of Boe is Jack Harkness. Similarly, the Torchwood Declassified featurette from Torchwood Series 2 has John Barrowman, David Tennant and Russell T Davies stating that they believe the Face of Boe is Jack Harkness. In-universe, however, we only have Captain Jack's testimony. [source]

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    There's no canon confirmation that he's the FoB
    – Valorum
    Aug 14, 2014 at 11:16
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    while he doesn't outright say it, he does say his nickname growing up was "the Face of Boe" because he grew up on the Boeshane Peninsula. his nickname is also mentioned here under "AS TIME AGENT AND CON ARTIST" tardis.wikia.com/wiki/Jack_Harkness and it's even listed as one of his aliases. I personally always thought that was the conclusion the show was leading to.
    – Madullah
    Aug 14, 2014 at 12:17
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    @Richard: I though it was undisputed. However, see the edit.
    – bitmask
    Aug 14, 2014 at 13:39
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    Russell T Davies said the issue was never meant to be settled: "I did spend a long time thinking about Jack’s immortality, and one day it occurred to me there was another immortal character on the show. It made me laugh. To be honest, on the screen, it’s couched in terms that are not absolute gospel. There are these spin-off books and comic books, and every now and then I’ll see a script for one where they say definitively that he’s the Face of Boe, and I always stop those from being printed. I have my own personal theories, but the moment it became very true or very false, the joke dies."
    – Hypnosifl
    Aug 14, 2014 at 15:54
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    @Hypnosifl: Not completely out of the question in a show that is primarily centred around time travel and its abuse to fix plot holes and have some fun.
    – bitmask
    Aug 14, 2014 at 16:27

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